1. Field of the Invention
The present invention relates to a data transmission system and a semiconductor circuit, and for example, relates to the data transmission system and the semiconductor circuit for transmitting data from an output buffer to an input buffer.
2. Background Art
There is an SSD (solid state drive) as a storage medium which is an alternative to a HDD (Hard disk drive). In recent years, to increase a storage capacity of the SSD, the number of memories trends to increase. When the number of memories increases, load capacitance of an input buffer increases, so that a slew rate of transmission data transmitted by an output buffer is degraded. To suppress the degrading of the slew rate, an internal series resistance value of a driver of the output buffer may be decreased, however, when the internal series resistance value becomes smaller, the ringing is induced because of reflections, and it becomes difficult to secure Signal Integrity.
Patent document 1 describes a circuit which reduces attenuation quantity of frequencies included in rising and falling waves of data, and enables high-bandwidth transmission by inserting a high-pass filter at a transmission terminal of a data transmission system.
Patent document 1: JP Patent Publication (Kokai) No. 2008-294837
However, in Patent document 1, it is an assumption that the load capacitance of the input buffer is a fixed value, so that when the load capacitance of the input buffer is changed, Patent document 1 cannot be applied. Particularly, when the input buffer is a memory LSI, memory capacity is frequently changed, so that when the load capacitance becomes smaller, the large ringing is induced in the wave. When the ringing is induced, a noise margin is reduced, so that the data transmission may become unavailable.
The present invention is implemented under consideration of the above problem, and provides the data transmission system and the semiconductor circuit in which it is possible to perform both of suppressing the degrading of the slew rate (suppressing the attenuation of the frequencies included in the rising and the falling of the data waves), and suppressing the ringing even when the load capacitance of the input buffer is changed.